I like this. It's easy to grasp, thematic, and gives everyone options no matter when they show up.

EDIT: And of course right after posting I think of something else I wanted to ask. Under this system, would it be possible to use your tokens to change a power into something different? Like, I'm not particularly invested in Amelie's Diamond Storm, and her Zygarde Forme ability is basically invalidated by shapeshifting being a freebie, so would I be able to save up four tokens to change them into something more appropriate to her character?